Recently, along with the trend of higher speed and lower power consumption of semiconductor device such as microcomputer and digital signal processor, electronic appliances for consumer use are more and more advanced in performance, while an electromagnetic interference which is an electromatic noise gererated from these electronic appliances is posing a serious problem. Accordingly, not only in electronic appliances, but also in semiconductor devices used in them, measures against electromagnetic interference are demanded. The most effective measure against electromagnetic interference in the semiconductor device is to install a capacitor of a large capacitance between the bias line and ground line inside the semiconductor device, hitherto the capacitor was placed outside the semiconductor device.
In addition, lately, nonvolatile random access memories in a simple construction having a capacitor, using a ferroelectric layer as capacitor dielectric layer, and dynamic random access memories having a capacitor using dielectric layer of high dielectric constant as storage capacitor have been developed.
A conventional semiconductor device having capacitor is specifically described below.
FIG. 1 is a partially sectional view of a representative semiconductor device. In FIG. 1, on a silicon substrate 1, an integrated circuit 6 represented by source/drain active areas 3, a gate oxide 4, and a gate electrode 5 is formed in a region enclosed by a field oxide area 2. Further on the silicon substrate 1, an insulating layer 7 is formed, and in a specific region on the insulating layer 7, a capacitor 11 consisting of a bottom electrode 8, a capacitor dielectric layer 9, and a top electrode 10 is formed. At least covering the capacitor 11, moreover, an interlayer insulating layer 12 is formed. There are also formed interconnections 14a connected to the source/drain active areas 3 through a first contact hole 13a, interconnection 14b connected to the bottom electrode 8 of the capacitor 11 through a second contact hole 13b, and interconnection 14c connected to the top electrode 10 of the capacitor 11 through a third contact hole 13c. Furthermore, a passivation layer 15 is formed in order to protect the interconnections 14a, 14b, 14c.
A manufacturing method of the conventional semiconductor device having capacitor shown in FIG. 1 is explained below while referring to the flow chart of manufacturing process shown in FIG. 2, together with FIG. 1. First, at step (1), the integrated circuit 6 is formed on the silicon substrate 1. At step (2), an insulating layer 7 is formed on a silicon substrate 1. At step (3), a capacitor 11 is formed on the insulating layer 7. This capacitor 11 is formed by sequentially laminating a first conductive layer as bottom electrode 8, capacitor dielectric layer 9, and a second conductive layer as top electrode 10, and patterning respectively by etching. As the capacitor dielectric layer 9, a ferroelectric layer or high dielectric layer is used, and as bottom electrode 8 and top electrode 10, a two-layer composition consisting of platinum layer and titanium layer sequentially from the side contacting with the capacitor dielectric layer 9 is used. At step (4), an interlayer insulating layer 12 composed of PSG (phos-silicate glass) is formed by CVD so that at least the capacitor 11 is covered. At step (5), a first contact hole 13a reaching the source/drain active areas 3 of the integrated circuit 6, a second contact hole 13b reaching the bottom electrode 8 of the capacitor 11, and a third contact hole 13c reaching the top electrode 10 of the capacitor 11 are formed. After forming interconnections 14a, 14b, 14c at step (6), a passivation layer 15 composed of silicon nitride layer or silicon oxynitride layer of high humidity resistance is formed by plasma CVD at step (7).
However, in such conventional semiconductor device having capacitor, a PSG layer is used as interlayer insulating layer 12, and although the purpose of alleviating the stress to the capacitor 11 is achieved, the moisture generated when forming the PSG layer by CVD is absorbed by the PSG layer, and this moisture diffuses into the ferroelectric layer composing the capacitor dielectric layer, thereby lowering the electric resistance. This phenomenon gives rise to increase of leakage current of the capacitor 11 or decline of dielectric strength, which may induce dielectric breakdown of the capacitor dielectric layer 9.
Yet, in such conventional semiconductor device having capacitor, as a passivation layer 15, silicon nitride layer or silicon oxynitride layer formed by plasma CVD is used, and although invasion of moisture from outside into the capacitor 11 may be prevented, activated hydrogen is generated in the layer forming process by plasma CVD, and this activated hydrogen may diffuse in the ferroelectric layer or high dielectric layer for composing the capacitor dielectric layer 9, which may induce increase of leakage current of the capacitor 11 or deterioration of electrical characteristic. Generally, the hydrogen atom content in the nitride layer formed by plasma CVD is as high as 10.sup.22 atoms/cm.sup.3, and by heat treatment after layer forming, diffusion of hydrogen into the capacitor dielectric layer 9 is accelerated, and the characteristic of the capacitor 11 is further degenerated.